The present invention relates to a three-dimensional acceleration sensor which can be used for an airbag actuated in the event of a collision of such a moving body as an automobile and for an active suspension in car body control.
A conventional three-dimensional acceleration sensor is described in, for example, 91CH2817-5/91, IEEE, 1991, pp. 655-658. The conventional sensor is finely worked through surface micro-machining. Structurally, it has a massive part and a central part provided inside the massive part, and the massive part is suspended by the central part and thin beams.
Since in the conventional apparatus the central part and the massive part are linked by only the thin beams, the sensor faces a problem of poor strength and is allowed to detect only acceleration values of approximately 1G to 2G.
Also, in the conventional sensor, the structure of gap and movable electrode is set up by removing all superfluous layers and consequently the gap is exposed externally, raising a problem that inflow of dirts and moisture to the electrode is inevitable.
An object of the present invention is to provide a three-dimensional acceleration sensor capable of detecting a large value of acceleration.
Another object of the invention is to provide a three-dimensional acceleration sensor which is constructed such that electrodes can be prevented from being deposited with dirts and the like.
To accomplish the above objects, in a three-dimensional acceleration sensor having a support on which a stationary electrode is arranged, a central part fixed to the support, a massive part acting as a movable electrode and a link member for interconnecting the central part and the massive part, the link member is comprised of a combination of diaphragms and beams which are provided around the central part.
Also, to accomplish the above objects in accordance with the present invention, in a three-dimensional acceleration sensor having a support on which a stationary electrode is arranged, a central part fixed to the support, a massive part acting as a movable electrode and a first link member for interconnecting the central part and the massive part, a frame is provided around the massive part, and the frame and the massive part are linked by a second link member comprised of a diaphragm.
According to the invention, in a three-dimensional acceleration sensor having a support on which a stationary electrode is arranged and a massive part acting as a movable part, a frame is provided around the massive part and the frame and the massive part are linked by a link member comprised of a diaphragm.
According to the invention, in a three-dimensional acceleration sensor having a support on which a stationary electrode is arranged and a massive part acting as a movable electrode, the distance between an electrode portion of the massive part and the stationary electrode is larger than that between the support and the massive part.
Since in the invention the central part and the massive part are linked by the diaphragms and beams, strength can be increased to permit detection of even an acceleration value of about 100G.
Further, since the outer frame and the massive part are linked by the diaphragm, inflow or invasion of dirts and moisture from the outside can be prevented to prevent erroneous operation of the massive part.